It is the job of the Project manager to define the brief. A project’s objective is to deliver outputs. To extract and cultivate these outputs is where the skill lies.
Project briefs should be agreed by all stakeholders at the beginning of the project, and it is important that the brief is regularly updated at key milestones within the project or when new information becomes apparent.
Revisiting the brief at key stages ensures that the building project that is eventually delivered meets the client’s requirements. This is even more important with more complex projects, the variables are higher and therefore more action is required to seek out these variables and manage risk.
The brief should be the "go to" document when there is uncertainty, it provides a high level view and should be worked back from to formulate the detail that is required to deliver the client requirements.
The brief should be clear in its wording and could lay out -
design and scope;
health and safety;
key performance indicators (KPIs);
risk analysis; and
any other constraints.
It is important for the project manager to refer back to the brief to ensure that the project is always inline with the brief and nudge the project team if they move outside the scope.